The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Direct conversion IQ-modulators are widely used in wireless communication transmitters to convert base band signals to radio frequency, since they are well suited to be implemented with integrated circuits.
Direct conversion IQ-modulators typically generate unwanted spectrum components in an up-converted signal due to the distortion in preceding transmitter stages and/or non-idealities caused by asymmetrical layout, for example. This leads to imbalance in quadrature channels, which results in unwanted image components in a modulator output. Additionally, an unwanted direct current (DC) offset at the modulator input causes leakage of a radio frequency (RF) local oscillator signal.
The unwanted leakage signals deteriorate signal-to-noise ratio of a signal at a receiver, thus limiting the efficiency of data transmission.